1. Field of the Invention
The present invention relates to a technique for processing a plurality of substrates by immersing the plurality of substrates in a processing solution stored in a processing tank. More particularly, the present invention relates to a technique for reducing the consumption of a processing solution in such processing.
2. Description of the Background Art
A substrate processing apparatus for performing a batch cleaning process on a plurality of substrates (or a batch of N substrates where N is a natural number not less than two) at the same time is used in a process step of manufacturing the substrates. Such a substrate processing apparatus performs the cleaning process in such a manner as to previously fill a processing tank which can accommodate a maximum number of substrates per batch to be transported thereto with a cleaning solution and to immerse a batch of N substrates actually transported thereto into the cleaning solution at a time.
The actual manufacturing process step, however, has presented a problem in that a maximum number of N substrates per batch are not always transported to the substrate processing apparatus. For example, a processing tank which can accommodate 50 substrates must be supplied with an amount of cleaning solution which fills the processing tank even for the cleaning of less than 50 substrates. Thus, there has been a problem such that the cleaning solution for 50 substrates is consumed even when less than 50 substrates are cleaned. In particular, this problem grows as a demand for the manufacturing of a wide variety of products in small quantities increases.